When my 2010 unibody mbp is running on battery and then the battery runs down to zero, instead of going to sleep the computer just acts like the power cord was pulled out on a desktop. In other words, if I leave my mbp turned on overnight when it's not plugged into the charger, then when I wake up in the morning my computer is totally powered off, and when I turn it back on a message says the machine shutdown unexpectedly and the system clock is reset to the year 1901. My main battery itself lasts for many many hours like its supposed to. Is there a backup motherboard battery that could be not working? How do I check that? And obviously that battery should still be working on a laptop that's less than 2 years old. How do I make it act like its supposed to so that the computer goes to sleep when it runs out battery instead of shutting down unexpectedly?